Solar Activity in the Past and the Chaotic Behaviour of the Dynamo

Abstract

The record of solar activity is reviewed here with emphasis on peculiarities. Since sunspot positions tell us a lot more about the solar dynamo than the various global sunspot numbers, we first focus on the records of telescopic observations of sunspots leading to positional information. Then we turn to the proxy record from cosmogenic isotope abundances, which shows recurrent grand minima over the last 9500 years. The apparent distinction between episodes of strong modulation, and intervening episodes with milder modulation and weaker overall activity, hints at the solar dynamo following a variety of solutions, with different symmetries, over the course of millennia.

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Acknowledgements

R. Arlt is grateful to the libraries of Leibniz Institute for Astrophysics Potsdam, the Royal Astronomical Society, and the Observatoire de Paris for permitting the digitization of observing records. N. Weiss gratefully acknowledges many discussions with Jürg Beer and Steven Tobias over the past two decades.